1. Field of the Invention
The present invention relates to a light emitting semiconductor structure and in particular relates to a light emitting semiconductor structure with at least two LED chips.
2. Description of the Related Art
Because light emitting semiconductor structure have several advantages over conventional lamps, such as a long lifetime, a small size, low power consumption, high response speed, etc., considerable research attention has been recently focused on development thereof.
Conventionally, one way to generate a white light emitting semicondcutor structure is to coat or fill a yellow phosphor on a blue LED chip. The blue light emitted by the LED chip is then mixed with the complimentary yellow light from phosphor to generate white light.
The other way to generate a white light emitting semiconductor structure is to mix different colors emitted from a plurality of the LEDs to produce a white light emitting diode. U.S. Pat. No. 7,005,667 discloses a light emitting diode, wherein a blue LED chip is arranged parallel to a blue-complimentary LED chip (such as yellow LED chip) to generate white light. However, two LEDs are arranged in the same plane and thus occupy too much area. Therefore, the package size of the light emitting semiconductor structure can not be reduced.
Therefore, there is a need to develop a light emitting semiconductor structure which has a small package size to simplify the design of the secondary optical lens in the subsequent steps.